You will find posts like yours in a continuous stream going back 6 1/2 years. And the answer is the same now as it was 6 1/2 years ago. Find the app that is stuck in a loop either sending data or attempting to and deal with it. A search of the forum will find plenty of tips for dealing with battery drain.

You will find posts like yours in a continuous stream going back 6 1/2 years. And the answer is the same now as it was 6 1/2 years ago. Find the app that is stuck in a loop either sending data or attempting to and deal with it. A search of the forum will find plenty of tips for dealing with battery drain.

But the point I'm making is that at home under wifi the same apps don't cause the power drain. So it is something particular to when it runs under LTE. Even with a 5-bar LTE. Should the power drain be so drastically different between wi-fi and LTE? The Apple specs indicate not. So I wonder what else is happening.

I did kill all apps and force a restart while outside, and then just checked mail and used Safari the whole train ride to test. But it still drained rapidly.

Are you using the Usage gauge or subjective measurements of battery life?

Cellular data requires between 60 mw and 500 mw depending on signal strength. WiFi requires 30 mw at any time. So even with a good signal cellular requires twice as much energy as WiFi when sending or receiving, up to 19 times with lower signal strength.

You also compared WiFi inside to LTE outside. What was the outside temperature? Lithium batteries lose capacity at low temperatures.

Are you using the Usage gauge or subjective measurements of battery life?

Cellular data requires between 60 mw and 500 mw depending on signal strength. WiFi requires 30 mw at any time. So even with a good signal cellular requires twice as much energy as WiFi when sending or receiving, up to 19 times with lower signal strength.

You also compared WiFi inside to LTE outside. What was the outside temperature? Lithium batteries lose capacity at low temperatures.

I was using the Usage guage.

You mention that "even with a good signal cellular data requires twice as much energy as WiFi when sending or receiving..."

"Internet use: Up to 8 hours on 3G, up to 8 hours on LTE, up to 10 hours on Wi-Fi"

That certainly suggests maybe a 20% hit for being on LTE. Not a 70% hit.

Well, first, it says Up to 8 hours... That means that 8 hours is the maximum, not the guaranteed results. Like fuel economy numbers. And like fuel economy, it matters a lot what you are doing with the phone. For example, are you using data continuously, or intermittently? Streaming music or video, for example, or using the Maps app, or using Safari continuously will use a lot more data (and thus energy) than playing Words with Friends, and will run the battery down faster. Apple doesn't know your usage pattern, so they assume a duty cycle for data.

A key difference between WiFi and cellular data is cellular uses power only when actively sending or receiving; WiFi uses power continuously as long as the phone is not asleep, whether sending, receiving, or neither.

Lawrence, Doug's issue is not not an app! I deleted every app on the phone except for the ones that apple wont let you delete and it didnt make a single bit of difference. It is also not normal so no point going into details of usage. Give people just a tiny bit of faith that they know their own usage and what is normal and not.

Doug, I had exactly the same issue as you. The ONLY solution that worked (and i tried everything) was a complete reset and setup as a new iphone. Do NOT install from backup. Manually reinstall everything, it will take 2-3 hours of your time but it is the only thing that works for your particular issue, (see my post a good few pages back).

"Internet use: Up to 8 hours on 3G, up to 8 hours on LTE, up to 10 hours on Wi-Fi"

That certainly suggests maybe a 20% hit for being on LTE. Not a 70% hit.

Well, first, it says Up to 8 hours... That means that 8 hours is the maximum, not the guaranteed results. Like fuel economy numbers. And like fuel economy, it matters a lot what you are doing with the phone. For example, are you using data continuously, or intermittently? Streaming music or video, for example, or using the Maps app, or using Safari continuously will use a lot more data (and thus energy) than playing Words with Friends, and will run the battery down faster. Apple doesn't know your usage pattern, so they assume a duty cycle for data.

A key difference between WiFi and cellular data is cellular uses power only when actively sending or receiving; WiFi uses power continuously as long as the phone is not asleep, whether sending, receiving, or neither.

Yes, there is always the "up to" fine print.

But if what you are saying about LTE use is true - that is uses twice as much energy in the BEST case as WiFi, then how can the advertised 80% of WiFi spec possibly be factual? Even under the best of circumstances?

Lawrence, Doug's issue is not not an app! I deleted every app on the phone except for the ones that apple wont let you delete and it didnt make a single bit of difference. It is also not normal so no point going into details of usage. Give people just a tiny bit of faith that they know their own usage and what is normal and not.

Doug, I had exactly the same issue as you. The ONLY solution that worked (and i tried everything) was a complete reset and setup as a new iphone. Do NOT install from backup. Manually reinstall everything, it will take 2-3 hours of your time but it is the only thing that works for your particular issue, (see my post a good few pages back).

I also notice that my iPhone 5 gets quite warm when used on the outside. Not something I experience at home under WiFi.

It seems when I first moved from my iPhone 4 to iPhone 5 I had a similar problem. The fix then was similar to your suggestion, but quicker and easier. I did do a complete reset and setup as a new phone. But I did install from a complete, encrypted backup from iTunes. That seemed to help then. Of course it was pre iOS 7.

But maybe I'll try that before trying the more time-consuming test you are suggesting.

But if what you are saying about LTE use is true - that is uses twice as much energy in the BEST case as WiFi, then how can the advertised 80% of WiFi spec possibly be factual? Even under the best of circumstances?

doug

Because, as I said, WiFi uses power continuously, but cellular only when actually exchanging data. Apple assumes that you are not exchanging data every second that you are using the phone. In addition, data exchange is not the only thing that uses power. Lighting the screen uses a lot of power. the CPU can use a lot of power if you are doing any sort of processing such as playing interactive games. Consider the numbers I gave. 60 mw at 5 bars is used by cellular data. The capacity of the battery is around 1800 mwh. So if data was the only thing using data you would get 1800/60 or 30 hours of battery life. But the spec only says 8 hours. 1800 / 8 is 225 mw/hr. If cellular is using 60 of it that means that other functions of the phone are using 165 mw/hr. This is the best case at 5 bars.

Power consumption goes up logarithmically, so even at 4 bars the power required by the cellular modem roughly doubles. And doubles again at 3 bars, etc. Bars are not a great measure, however, as they are very approximate. If you put the phone in diagnostic mode it will display in dbm instead of bars. This is a number you can make more accurate cellular power demand calculations with if you really want to.

To address your observation that restoring the phone as new reduces battery consumption. This means that you had an errant app. Note that you cannot kill all background processing. Killing an app in the Quick Launch screen does NOT always kill background processes. The built in apps such as mail, messages, calendars, etc have background processes that can not be killed. Period. Any app that can accept notifications can start a background process that will not show up in the quick launch screen. Restoring the phone kills all background apps. So does running the battery down until the phone shuts off.

But if what you are saying about LTE use is true - that is uses twice as much energy in the BEST case as WiFi, then how can the advertised 80% of WiFi spec possibly be factual? Even under the best of circumstances?

doug

Because, as I said, WiFi uses power continuously, but cellular only when actually exchanging data. Apple assumes that you are not exchanging data every second that you are using the phone. In addition, data exchange is not the only thing that uses power. Lighting the screen uses a lot of power. the CPU can use a lot of power if you are doing any sort of processing such as playing interactive games.

I just want to address this point for the moment. In the stated specs, Apple is assuming exchanging data every second I'm using the phone because it clearly states those battery times are "Internet use." Unless they want to have some Clinton-esque debate over "what the meaning of 'is' is." Internet use would imply to anybody that that is the exchange of data over the Internet I think.

As far as screen lighting and cpu, those would be the same on wifi and off. Everything else should be equal, other than whether I'm connected to LTE only or to WiFi.

Lawrence, our problem is not caused by an app. It is something bug in the software controlling the 3G/4G. It is not an issue about normal power usage 3G/4g vrs Wifi or even lighting or any other battery saving measure and it is a pointless exercise just serving to fluff up the thread even mentioning those things. Our phones rapidly drain battery with everything closed and the screen switched off.

The solution is wiping the phone and setting it up again as a new phone.

Doug, definitely backup up your phone before you wipe it just incase but make sure you do not restore your phone from that backup. All my contacts, calendars and emails were in Microsoft outlook so they just jumped across when i set that up. Music and apps have to be brought across manually.

Im starting to believe that the iPhone 5 have some really hardware issues because today, while downloading a 350MB file and after a full charge, my battery went from 100% to 1% in a matter of minutes (everything over Wi-fi with the carrier internet turned off).

Now the problem is, how can I show to my carrier (wheres the phone it's locked), that I have a faulty device?

Because the only thing they do it's a full reset and give me back the same phone, saying that they didnt find anything wrong. A think that I did already over and over...without restoring any backup!

Before anyone replies telling me how they fixed their phone by doing <insert any variables here> please know I already did. I have been following this thread since the original post and myself, along with many others, are still struggling with the same issue.

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